
class Circle {
//创建对象
//以一个圆为对象
//设置随机的 x，y坐标，r半径，_mx，_my移动的距离
//this.r是创建圆的半径，参数越大半径越大
//this._mx,this._my是移动的距离，参数越大移动
constructor(x, y) {
  this.x = x;
  this.y = y;
  this.r = Math.random() * 6;
  this._mx = Math.random();
  this._my = Math.random();

}

//canvas 画圆和画直线
//画圆就是正常的用canvas画一个圆
//画直线是两个圆连线，为了避免直线过多，给圆圈距离设置了一个值，距离很远的圆圈，就不做连线处理
drawCircle(ctx) {
  ctx.beginPath();
  //arc() 方法使用一个中心点和半径，为一个画布的当前子路径添加一条弧。
  ctx.arc(this.x, this.y, this.r, 0, 360)
  ctx.closePath();
  ctx.fillStyle = 'rgba(255, 255, 255, 0.3)';
  ctx.fill();
}

drawLine(ctx, _circle) {
  let dx = this.x - _circle.x;
  let dy = this.y - _circle.y;
  let d = Math.sqrt(dx * dx + dy * dy)
  if (d < 180) {
	ctx.beginPath();
	//开始一条路径，移动到位置 this.x,this.y。创建到达位置 _circle.x,_circle.y 的一条线：
	ctx.moveTo(this.x, this.y); //起始点
	ctx.lineTo(_circle.x, _circle.y); //终点
	ctx.closePath();
	ctx.strokeStyle = 'rgba(236,232,25, 0.4)';
	ctx.stroke();
  }
}

// 圆圈移动
// 圆圈移动的距离必须在屏幕范围内
move(w, h) {
  this._mx = (this.x < w && this.x > 0) ? this._mx : (-this._mx);
  this._my = (this.y < h && this.y > 0) ? this._my : (-this._my);
  this.x += this._mx / 2;
  this.y += this._my / 2;
}
}

//鼠标点画圆闪烁变动
class currentCirle extends Circle {
constructor(x, y) {
  super(x, y)
}

drawCircle(ctx) {
  ctx.beginPath();
  //注释内容为鼠标焦点的地方圆圈半径变化
  //this.r = (this.r < 14 && this.r > 1) ? this.r + (Math.random() * 2 - 1) : 2;
  this.r = 8;
  ctx.arc(this.x, this.y, this.r, 0, 360);
  ctx.closePath();
  //ctx.fillStyle = 'rgba(0,0,0,' + (parseInt(Math.random() * 100) / 100) + ')'
  ctx.fillStyle = 'rgba(255, 77, 54, 0.6)'
  ctx.fill();

}
}

//更新页面用requestAnimationFrame替代setTimeout
window.requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;

let canvas = document.getElementById('canvas');
let ctx = canvas.getContext('2d');
let w = canvas.width = canvas.offsetWidth;
let h = canvas.height = canvas.offsetHeight;
let circles = [];
let current_circle = new currentCirle(0, 0)

let draw = function() {
ctx.clearRect(0, 0, w, h);
for (let i = 0; i < circles.length; i++) {
	circles[i].move(w, h);
	circles[i].drawCircle(ctx);
	for (j = i + 1; j < circles.length; j++) {
		circles[i].drawLine(ctx, circles[j])
	}
}
if (current_circle.x) {
	current_circle.drawCircle(ctx);
	for (var k = 1; k < circles.length; k++) {
		current_circle.drawLine(ctx, circles[k])
	}
}
	requestAnimationFrame(draw)
}

let init = function(num) {
for (var i = 0; i < num; i++) {
	circles.push(new Circle(Math.random() * w, Math.random() * h));
}
	draw();
}

window.addEventListener('load', init(60));

window.onmousemove = function(e) {
	e = e || window.event;
	current_circle.x = e.clientX;
	current_circle.y = e.clientY;
}

window.onmouseout = function() {
	current_circle.x = null;
	current_circle.y = null;
}
